The compound has a reputation as a party drug, but ketamine is increasingly being studied for its potential use as a rapid-fire treatment for depression. In people who live with the disease, thoughts of suicide can strike suddenly and without warning. Fast-acting, successful interventions are hard to come by.

But a spate of recent research suggests that ketamine could provide quick and powerful relief — even to people whose depression has repeatedly failed to respond to other medications and to those who are suicidal.

Experts say they're onto something promising. In a field that hasn't seen a new class of drugs in nearly four decades and in which patients are often desperate and suicidal, that kind of sentiment holds a lot of weight.

"Imagine arriving in the emergency room with severe pain from a kidney stone — pain so bad that you can't think. You'll do anything to make it go away. And the doctors say, 'here's a drug that we've been using for 30 years, it works 50-60% of the time, and it should start to work in 4-6 weeks'" Cristina Cusin, a psychiatrist at Massachusetts General Hospital and an assistant professor at Harvard University, told Business Insider. "That's currently the best we can do" for someone who is suicidal.

Cusin co-authored a large new review of the existing research on ketamine that was published this month in the Harvard Review of Psychiatry. Her findings shed light on the need for new treatments, but she also advises caution for patients.

"We are just scratching the surface of the mechanisms of action with ketamine," Cusin said.

Trying to tackle a uniquely troubling problem

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For her review, Cusin looked at almost 40 ketamine studies that involved brain imaging.

Cusin faced challenges in assembling very different studies into one review, but she came up with some key takeaways. For one, she observed that people given ketamine experience measurable brain changes — many of them in areas that have been tied to our ability to process and regulate emotions.

Ketamine also appeared to increase activity in parts of the brain linked with reward processing, which would help to explain some of its antidepressant effects.